Digital data storage devices have been developed in many different formats. Recent years, CDs (compact discs) and DVDs (digital video discs) have been popular data storage devices as recordable and prerecorded media. There are even smaller versions of CDs and DVDs and called mini CDs and mini DVDs. But these data storage media require hardware such as hard (laser) disc drives to write or retrieve data. And because the disc drives have to accommodate these large storage media and require moving mechanical parts and laser sensors, they are relatively large in size.
The more recently developed static blank digital media called flash memory drives typically found in digital cameras, MP3 players, camcorders and the like are smaller in size and have become popular. There are several commercial product formats such as Compact Flash, SD and XD cards, etc., but all of these utilize flash memory chips as storage memory and they have no moving mechanical components. One type of such flash memory chip storage media that is popular with personal computer are Universal Serial Bus (USB) flash memory drives. The USB flash memory drives are plug-in devices configured to be plugged into the USB port of a personal computer and data can be stored in and retrieved from them.
The USB flash memory drives have the standard USB Type A connector at one end for plugging into the USB Type A port socket on computers and one, sometimes two, PCBs forming the reminder of the device. The one or more PCBs have the necessary electronic components thereon, such as the flash memory chip and the associated controller circuit devices. The PCBs are of conventional construction with printed circuitry (i.e. conductive lines and through-vias, etc.) connecting the various electronic components.
There are a number of conventional ways the USB connector end of the USB flash memory devices are formed. In one of the conventional construction, the contact terminals or pads in the USB connector is formed by pressed metal contact pads soldered onto an end of a PCB sized to fit into a USB Type A socket. The PCB is where the memory chip(s), controller IC, and other supporting electrical components for the flash memory device are installed. The terms “terminals” or “pads” will be used interchangeably in this document to generically refer to metallized areas on a PCB that are intended for temporary or permanent electrical connection with other structures. Such electrical connections may be made by mechanical contact, solder joint, or any other suitable type of attachments used in the electronics packaging industry. In another conventional construction, the contact pads for the edge connection are formed directly on the PCB as an extension of the printed circuit metallurgy on the PCB. The contact pads are patterned along the edge of the PCB and sufficient portion of the pads are exposed for making contact. Typically, the printed circuit metallurgy on PCBs have copper as the base metal and the exposed portions of the contact pads are plated with nickel then gold. These conventional construction methods are utilized in previously mentioned data storage media products such as USB flash memory drives, Compact Flash, SD and XD cards, for example.
One of the disadvantages of the conventional edge connection contact constructions discussed above is that a substantial portion of the limited space on the PCB is taken up by the edge connection contact pads. Thus, the space necessary for all of the printed circuitry (i.e. the wiring) necessary to interconnect the various electronic devices on the PCB must come from the remainder of the PCB. This places limits on the product designer's ability to make the PCBs for the computer plug-in devices such as the flash memory devices small as possible. Therefore, there is a need for a new advance in the electronic packaging technology that will provide the product designers the ability to shrink the PCBs further to meet the demands of the consumers' desires for smaller, more convenient and attractive products.
You can not reduce the total thickness of contact terminals less than 1.9 mm or more than 2.3 mm because of the given dimensions for adopting USB port. The tolerances of the thickness of contact terminal for USB drive are less than 2.4 mm and greater than 2 mm. With these restrictions, you can not install any parts on the PCB right behind of the contact terminals, which will create short circuit with USB port (Drawing B-3). The space between the contact terminal and the main part of the pcb on the terminal side can not be raised for the length of 9.5 mm from the end of the terminal side. Re Drawing B”—Remarks; You can not use the spaces B-4 not only for the 1) any electrical parts but also 2) any patterns lines and/or via holes for the fear of short circuiting with the usb port when inserted. Or it simply can not fit into the usb port because of the height if parts were soldered on the main pcb.